This paper presents articulatory and acoustic data of tongue root contrasts in Khalkha Mongolian, comparing acoustic cues in F1 and F2 to measurements of tongue root position from 3-D/4-D ultrasound imaging. The primary acoustic cue of + ATR across languages is decreased F1 (Stalwart, 2008), with various effects on F2 and F1 bandwidth found in the literature. Washington (2016) found that Kyrgyz and Kazakh covary ±ATR and ±back, with + ATR,-back marked by increased F1 and decreased F2, based on acoustic and ultrasound data. Khalkha Mongolian contrasts −ATR, + back vowels both with + ATR, + back, conditioned by vowel harmony; and + ATR, −back vowels, conditioned by palatalized consonants. This paper compares formants of these three classes of vowels with measures of tongue root position, taken from 3-D/4-D Ultrasound images of 6 Khalkha speakers. Comparisons of formants of these three classes of vowels, correlated with tongue root measurements, make clear the acoustic correlates of tongue root advancement in vowel formants. The + ATR, + back vowels are marked by decreased F1, while the + ATR, −back vowels show decreased F1 and increased F2.
Joshua Sims (Tue,) studied this question.